Collaborative study was undertaken at Bicetre and at Northwestern University Medical Center (Chicago), to identify the nature and cellular distribution of steroid receptors in the isolated cell types of BPH. In Bicetre, technics for specific "enzyme" markers have been developed and are correlated with morphometric evaluation of BPH slices, and applied to prostatic cell types. Optimal methods for the quantitation of steroid receptors, intended to avoid inactivation of receptor sites produced by incubation of cell subfractions under "exchange" conditions, will be investigated. Once developed, they will be applied to BPH samples both at Bicetre and Chicago, and correlated with cell morphology and marker enzyme assays.